When vascular smooth muscle cells are cultured, in vitro, they lose their contractile response to vasocontractile substances. This phenotypic modulation greatly limits vascular medical research to animal and animal organ experimentation, especially in such fields as hypertension. While some indirect information can be obtained from non-contracting smooth muscle cell cultures, results of such experiments must be carefully interpreted. Furthermore, even though it is possible to obtain contractile smooth muscle cells in vitro, if they are freshly isolated (primoculture), this technique is limited by the number of cells obtainable and clinically available human tissue.
The various methods described, up until now, to evaluate contractile responses of smooth muscle cell cultures have three common and serious weaknesses: 1) the cells are on non-physiological substrata, 2) quantitative evaluation of contraction forces are not possible, and 3) quantitative assessment of contraction is made on a "single-cell basis" (although numerous cells can be studied concurrently) and therefore, does not necessarily provide information on a "tissue basis" response. Recently, some two-dimensional sub-cultures of non-vascular animal smooth muscle cells have shown limited contractile responses to appropriate stimulants. Nevertheless, human sub-cultured smooth muscle cell contraction in particular cells of vascular origin, has yet to be demonstrated.
Consequently there is a need to develop a smooth muscle cell construct that can be useful as an in vitro replica of smooth muscle responses in vivo.